This is clearly where they justify the money:Case: Comes with Custom Daniel Defense Full-Latch Impact Plastic Case

You can't compare 5.56 to 300blk by any standard of measure. I had a hard-on for a few months to build a 300blk upper strictly for hunting in lieu of buying a 30cal bolt gun, and realized I was kidding myself.

My current take on 300blk:
Subsonics: might as well buy a 1911 with lasergrips.
Supersonics: for the price of an upper, get a Ruger American in .308 instead.

MATERIALS & CONSTRUCTION
Precision crafted from the highest quality material available today with meticulous attention to detail, The Daniel Defense M4 Carbine will prove to be the benchmark in the industry.